How to render small object, as pixel art, without losing any of the pixels (Cycles render)?
I would render at some multiple of the target pixel dimensions, and then take it into Photoshop.  Edit the original and/or the downsampled result to get the features you want.  For something that small, with just a few missing details, just paint it in using the pencil tool: turn anti-alised smudges into crisp (oversized) blocks; adjust the location of an edge so it downsamples nicely; etc.